The frequency and timing of epileptiform activity on continuous electroencephalogram in comatose post-cardiac arrest syndrome patients treated with therapeutic hypothermia

Abstract

Aim: The incidence and timing of electrographic seizures and epileptiform activity in comatose, adult, post-cardiac arrest syndrome (PCAS) patients treated with therapeutic hypothermia (TH) have not been extensively investigated. We hypothesized that onset most frequently occurs within the first 24 h post-arrest and is associated with poor neurologic outcome.

Methods: Single-center, retrospective analysis of a cohort of 38 comatose PCAS patients treated with TH and continuous-EEG-monitoring (cEEG), initiated as soon as possible after ICU admission. All raw cEEG waveform records were cleared of annotations and clinical information and classified by two fellowship-trained electroencephalographers.

Results: Twenty-three percent (9/38) of patients had electrographic seizures (median onset 19 h post-arrest); 5/9 (56%) had seizure-onset prior to rewarming; 7/9 (78%) had status epilepticus. Forty-five percent (17/38) had evidence of epileptiform activity (electrographic seizures or interictal epileptiform discharges), typically occurring during first 24 h post-arrest. Interictal epileptiform activity was highly associated with later detection of electrographic seizures (6/14, 43%, p=0.001). Ninety-four percent (16/17) of patients with epileptiform activity had poor neurologic outcome or death at discharge (Cerebral Performance Category scale 3-5; p=0.002) as did all (9/9) patients with electrographic seizures (p=0.034).

Conclusions: Electrographic seizures and epileptiform activity are common cEEG findings in comatose, PCAS patients treated with TH. In this preliminary study, most seizures were status epilepticus, had onset prior to rewarming, evolved from prior interictal epileptiform activity, and were associated with short-term mortality and poor neurologic outcome. Larger, prospective studies are needed to further characterize seizure activity in comatose post-arrest patients.

Fig. 1

(a) Generalized epileptiform activity with myoclonus artifact labeled as seizure. Varying frequency (1-3 Hz) GPEDs appearing during the course of prolonged epileptiform activity labeled as seizure. The patient had torso and face myoclonus noted. (b) Left posterior quadrant discrete electrographic seizure activity, occurring repetitively, lasting for 30–60 s at a time, over a 24 h period.